1. Field of the Invention
The present invention relates to a color processing method that sets viewing conditions based on shooting conditions, a program thereof, and an image pickup apparatus.
2. Description of the Related Art
Conventionally, color matching among different devices is generally made in such a method as is shown in FIG. 6.
Specifically, input data such as RGB data is converted into XYZ data in a device-independent color space by using an input profile 601. Next, a color outside a color gamut of an output device cannot be expressed by the output device. Therefore, color gamut mapping in a PCS 602 converted XYZ data into mapped XYZ data within the color gamut of the output device. Then, the mapped data is converted from the XYZ data in device-independent color space to CMYK data in device-dependent color space by using the output profile 603.
However, it is difficult to perform color matching under different viewing conditions. A human color appearance model must be introduced so that color matching is realized under different viewing conditions.
The human color appearance model is designed so that human color appearance may be estimated accurately when a color patch of a viewing angle 2° is given, and defines a human field of view, as is shown in FIG. 4. Generally, a standard colorimetric observer 401 in CIE 1931 color system has an applicable range at a viewing angle 1° to 4°, therefore this applicable range field is divided into a stimulus field 402 below a viewing angle 2° and an adjacent field 403 below a viewing angle 4°. Then, the field between the adjacent field 403 at a viewing angle 4° and a field at a viewing angle 10° is called a background field 404, and a field surrounding the background field 404 is called a surrounding field 405. Furthermore, a field of vision consisting of the stimulus field 402, the adjacent field 402, the background field 403, and the surrounding field 404 is called an adaptation field 405.
Typical color appearance models such as CIE CAM97s and CIE CAM02 define the viewing condition parameters necessary to convert a relative XYZ value of a color patch into a JCh value or QMh value on the color appearance space independent from viewing conditions.
Next, input and output viewing conditions being considered, a color matching method performed among different output devices will be described with reference to FIG. 7. FIG. 7 is a view which is useful in explaining the color matching among different output devices, considering input/output viewing conditions. A light source on the input side is D50, and a light source on the output side is A.
First, the input data such as the RGB data under a D50 light source is converted into XYZ data under the D50 light source by using an input profile 21.
Next, the converted XYZ data is subjected to the forward conversion of a color appearance model according to the input side viewing conditions in a CAM 22, and then is converted into JCh data 23 or QMh data 24 in color space independent from the viewing conditions. Then, the gamut mapping is performed to the JCh data 23 or QMh data 24. The JCh data 23 or QMh data 24 is subjected to inverse conversion of the color appearance model according to the output side viewing conditions in CAM 25, and then is converted into XYZ data under an “A” light source. The XYZ data under the light source of output viewing conditions (the “A” light source) is converted into CMYK data under “A” light source by using the output profile 26. (Refer to Japanese Laid-Open Patent Publication (Kokai) No. 2000-050086 (U.S. Pat. No. 6,542,634), for example).
Conventionally, there has been another problem that it is a user that needs to set input and output viewing condition parameters through a user interface, which is too complicated for an average user to understand. A method in which viewing condition parameters for each viewing condition are pre-stored in a profile in order to facilitate the user setting, and a user needs to choose one of the pre-stored viewing condition parameters has also been used
However, it is difficult to properly set the viewing condition parameters for an image shot by a digital camera because the viewing conditions at a shooting place are unclear, and the shooting conditions are different.